xc90 Transmission Service Required ECM-5310 & TCM-002F

[MissSpentYouth]

Hi All,

I am just trying to sort a problem I have with my xc90 d5 auto 2004.

If I drive it for a bit and then decelerate in 5th I get Transmission Service Required pop up followed a short while latter by a jolt as the box locks itself into 4th gear as a sort of limp home mode to protect itself from overheating. Display changes from D to -- hill starts become problematic and very slow to pull away. If you stop and turn it off and back on again then you can get back to normal operation albeit with the message in the display.

Gearbox works perfectly up until that point.

Codes from Veda are -

ECM-5310 communication error with TCM - Communication fault
TCM-002F lock-up function slipping or not engaged

If I clear the codes the 002F goes but 5310 remains.
If I pull the TCM out of its socket and replace it then I can clear 5310.

Both codes return after a drive when I get the Transmission message pop up.

So far I have cleaned the 3 solenoids in the valve body and flushed the transmission fluid. This seemed to make shifting worse but I couldn't complete the adaptions process that well due to the above fault. Then replaced the valve body with a new one, now shifts like a new car. Swapped the TCM for a known good unit. None of the above made a difference.

Don't know whether to focus on 5310 which tells me ECM and TCM have issues talking to each other on the CAN bus, I think I will pull both and try and clean the connectors and sell if I can get to the back of them. This seems unlikely to be my problem as they are sat right next to each other in a dry box.

Or focus on 002F which says there is a speed discrepancy between two sensors which should be locked together.

I think I need to try and read the codes after I get the Message but before it bangs into 4th as 002f might be a result of this harsh emergency shift.

Maybe also need to investigate the reported oil temperature as this lock down into forth is a designed feature of the box if the oil temp gets to high.

There are a number of posts on the internet for this exact fault but no one seems to have fixed it.

The oil was very dark but did not smell burnt prior to the flush. The car does have a tow bar so may have done caravan work in the past.

Any help much appreatiated

[MissSpentYouth]

Just to add the car will accelerate flat out from rest up through the gears perfectly with no noticeable slipping so seems odd that it is when simply coasting at 50 in 5th that the message pings up.

If I drive round like a granny then all is well.

Makes me think I have a temperature sensor that is over reading or for some reason my oil is overheating triggering this fail safe mode. that doesn't tie in with the codes though as they should then surely read transmission overheated of some such thing.

Could also try driving it in manual mode and see if that changes things

[SwissXC90]

Why not connect VIDA and graph / log the temperatures during a drive?

[MissSpentYouth]

Spent some more time on the car yesterday.

It always does it when coasting with no throttle at about 50 miles an hour down a slight incline.

Temperature of transmission fluid seems fine.

Pulled the TCM and ECM and checked out all the wiring all good.

Next job is to check the wiring from the TCM to the transmission

Cant see how the ECM loses communication with the TCM when they are sat next to each other in a box connected by one twisted cable pair.

I have tried a known good TCM and just the same....

[gmonag]

50mph is significant because that is the speed (and above) at which the transmission locks.

[The vast minority]

Very interesting thread, it sounds electronic to me just as it does to you. The oil can't be overheating in the circumstances you are describing so id be thinking sensor faults or wiring fault somewhere. Having towed a caravan or not in the past shouldn't be much of a worry, if its broken its broken if its not its not and yours sounds like it is mechanically perfect with this annoying electronic fault.

Good luck with the cure and please post your findings.

Al

[Tannaton]

I think you will find that it's third gear it's going into - this is the standard emergency gear. You would get a warning on the dashboard if the oil temperature was too high, I don't think this causes the limp mode but aren't sure.

As has been said the clue here is that around 50-55 mph is when the torque converter locks in 5th, the problem seems to be it can't hold the lock on overrun - i.e. When the transmission is turning the engine, not the other way around. This is measured by two speed sensors which are on the outside of the box - one for the input shaft and one on the differential output. When you accelerate through 50 mph and beyond in 5th do you notice that the revs drop at some point and then remain proportional to road speed with no flare on power up?

I would suggest that you do some more testing with the gearbox in manual / geartronic mode, that way you get additional TC lock at 30 in 3rd and 40 in 4th - so select 3rd gear and accelerate to say 40 and lift off.... etc.

I also think the ECM code is a red herring, I've seen this before but you fix the gearbox and all is well again. You can also test the wiring from the TCM to the gearbox using VIDA, and specifically the TC lockup solenoid, but any bad connections or short circuit would have resulted in a very specific error code.

You have already done just about everything I can think of, it does sound like the TC lockup mechanism within the gearbox is worn or damaged - probably time to start talking to a transmission specialist?

[MissSpentYouth]

Thanks guys your suggestions most helpful.
Struggling to get the time to spend on this at the minute.
I did try driving it in manual mode in 5th and coasted and it pinged up with the error message just like in Drive.
I will try and get out in it and do some more testing with other gears and see if it is always same gear same speed etc.
Never seems to have any problems accelerating or cruising it is when coasting or slowing down.
When slowing down locked in 5th it must unlock at some point prior to shifting into 4th what speed does it do that at ?
Will also look at the valve body solenoids using VIDA and also buzz them out from the TCM connector with a multimeter and check I see the correct resistance.
Agree with what you say Tannaton, I think the 5310 code is a red herring, I will check the TCM to solenoid wiring but if that was dodgy I would expect more specific codes, I tend to agree that I must have a worn lock up mechanism in the main gearbox that can cope with forward torque but not reverse.
Is the lock up mechanism basically a wet multiplate clutch operated by the TC lockup solenoid ?
When I put the new valve body in I did not renew the two rubber O rings were it connects to the gearbox maybe they are leaking and causing loss of line pressure, they did look OK though.

[gmonag]

When slowing down locked in 5th it must unlock at some point prior to shifting into 4th what speed does it do that at ?

50mph

You can feel it happen as you coast down past 50mph; the car feels as if you have just released the brakes,

[Tannaton]

Originally Posted by MissSpentYouth

Will also look at the valve body solenoids using VIDA and also buzz them out from the TCM connector with a multimeter and check I see the correct resistance.

VIDA will do that for you if you look in the right place....